1. Field of the Invention
This invention relates to a power amplifier, and more particularly to a power amplifier which has a muting circuit to drive the power amplifier into a muting condition when an excessively large signal is supplied to it.
2. Description of the Prior Art
One of the problems in the design of transistorized power amplifiers is that a surge current of extremely large amplitude flows through the power transistors and load immediately after the power amplifier is brought into operation. This results in noise or other undesired phenomena in the load, and, sometimes, in destruction of the power transistors and the load. Another problem is than an excessively large input signal causes the power transistors or the load to be overloaded, possibly causing their destruction.
The use of muting circuits is known in the art of designing power amplifiers to prevent the occurrence of undesired noise or other phenomena and the destruction of the power transistors and the load. This is accomplished by inserting an electronic control switch in the current path of an amplifying transistor located before the power transistors. In such designs, the electronic control switch does not completely render the amplifying transistor dead. Thus part of the input signal passes through the amplifying transistor to the power transistors when a large signal is supplied, causing noise or other undesired phenomena, although at a relatively lower level than when the electronic control switch is not used.